The present invention relates to ink jet recording apparatus provided with a recording head for ejecting ink drops in accordance with print data. More particularly, the invention relates to a management technique which solves a problem arising from executing a flushing operation to idly eject ink drops to a capping member for hermetically closing a nozzle formation face of the recording head, and which suppresses the solidification of the ink and the like within the capping member by appropriately managing a flushing amount.
Generally, the ink jet recording apparatus is provided with the ink jet recording head for receiving ink from ink cartridge, and a sheet feeder for moving a recording sheet of paper relative to the recording head. An image is recorded on the recording sheet in a manner that ink drops are ejected onto the recording sheet in accordance with print data while moving the recording head in the main scanning direction. In the recording head, to print, ink is pressurized within a pressure generating chamber and ejected in the form of ink drops onto the recording sheet through the nozzle orifices. Therefore, the nozzle orifices are frequently clogged, and this results in improper printing. Various causes of the nozzle clogging exist, and examples of them are increase of ink viscosity due to solvent evaporation through the nozzle orifices, ink solidification, dust adhesion to the orifices, and entering of air bubbles.
To avoid the clogging trouble, this type of the ink jet recording apparatus uses a capping member for hermetically closing the nozzle formation face of the recording head in a non-print mode. The capping member serves as a lid for preventing the ink at the nozzle orifices of the recording head from being dried. Further, it serves to recover the ink drops ejection ability of the recording head. That is, when the nozzle orifices are clogged, the nozzle formation face is sealed with the capping member, a negative pressure is applied from a suction pump to the clogged nozzle orifices to forcibly suck the ink therefrom. In this way, the clogging of the nozzle orifices is removed.
A process of forcibly sucking the ink from the clogged nozzle orifices, which is executed for removing the clogging of the recording head, is called a cleaning operation. It is executed when the printing is started again after a long power-down time of the apparatus or when the user recognizes printing failure and operates a cleaning switch, for example. In the cleaning operation, under negative pressure generated by the suction pump, the ink is sucked into the capping member from the recording head, and then the nozzle formation face is wiped out with a wiping member formed of a rubber material, for example.
A drive signal, which is not related to the printing, may be applied to the recording head, thereby causing the recording head to eject ink drops. This operation is called a flushing operation. Uneven meniscuses at the nozzle orifices of the recording head are reshaped into the original states through the wiping operation by the wiping member. In the nozzle orifices which are infrequently used for ejecting ink drops during the printing operation, the ink located thereat is likely to increase its viscosity. Accordingly, those nozzle orifices are frequently clogged with the ink of increased viscosity. To avoid this, it is periodically executed.
Meanwhile, the flushing operation is executed to prevent the nozzle orifices having a less chance of ejecting ink drops during the printing operation from being clogged, as mentioned above. Additionally, it is executed for preventing the nozzle orifices from being dried when the recording head is out of operation by moistening the ink absorbing member located within the capping member with the ink.
Recently, the printing has been diversified, and use of the ink containing pigment is a trend in this field. Further, a technique also exists which adds surfactant to the ink composition in order to quicken the fixing of the pigment onto the recording sheet. In the pigment contained ink, a problem that bubbles are generated in the capping member arises. The generated bubbles will destroy the meniscus formed at the nozzle orifices, so that ejection failure occurs. A possible means to avoid the printing trouble of the recording head owing to such ink bubbles is to deepen the capping member to have the deep inner bottom part so that the ink bubbles are away from the nozzle formation face.
In a case where the capping member having the deep inner bottom part is employed, the following problems arises anew. When the flushing operation is executed, ink drops ejected from the nozzle orifices are impeded by air resistance and the like during their flight, and transformed into finer ink drops (ink mist) since a distance between the nozzle formation face and the bottom part of the capping member is large. The ink mist tends to leak out from the space defined between the nozzle formation face of the recording head and the capping member, and floats within the recording apparatus.
The ink mist floating within the apparatus stick to the guide rod for moving the carriage or the like, soils the same, thereby making the carriage movement difficult. Further, the ink mist soils other mechanisms. As a result, the normal operation of the recording apparatus is lost. The ink mist also soils the recording sheet under printing.
A specific color ink of the pigment-contained ink is easy to solidify at a specific position within the capping member, through the repeated flushing operations. In an extreme case, the solidified ink is accumulated into a mountain-like shape. When the recording head is sealed with the capping member, there is a chance that the accumulated ink reaches the nozzle formation face.